Title

Dairy Curds

Broad Question

What dairy product curdles most?

Specific Question

How does the percentage of fat in dairy products affect the rate it curdles at and the amount of curds it produces?

Hypothesis

It is hypothesized that the heavy cream will produce the most curds. This is hypothesized because heavy cream has the highest percent of milk fat out of all seven dairy products.

Graph of Hypothesis

Variables

Independent Variable:

Different dairy products

Dependent Variable:

Amount of Curds

Variables That Need To Be Controlled:

Amount of dairy product, amount of time, temperature of storage area, container product curdles in, brand of dairy product, same scale, and same cheesecloth.

Vocabulary List That Needs Explanation

curds - soft white lumps made of casein proteins in dairy products, forms when milk goes bad
casein and whey proteins - two types of proteins found in dairy products; casein proteins become solid, called curds, whey proteins remain a liquid, called whey
pasteurization - process of killing micro-organisms and kill pathogens so the dairy product is less likely to cause disease
pathogens - germs

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General Plan

An experiment was conducted to determine what dairy product produces the most curds. The general plan for the experiment was to make 3 glasses of 1 cup each of the following dairy products: skim milk, 1% milk, 2% milk, whole milk, fat free ½ & ½ , regular ½ & ½ and heavy cream. The cups sat together in the boiler room at school, in one cardboard box with a lid. After one week of time, one cup of each liquid was drained and the amount of curds was then measured by dumping the contents of the cup through a cheesecloth and into a bucket, separating the curds and whey. The remaining curds were then weighed on a scale, and the data was recorded. After another week, two weeks in total, the process was repeated with the second cup. And after three weeks, the same was done with the final cups. Each dairy product was then graphed to see which dairy product produced most curds and to compare the rates and amounts. The amounts of curds produced was determined by adding all three week’s curds to create one weight.

Potential Problems And Solutions

problem : where to conduct experiment
solution : teacher found school boiler room that could be used

Safety Or Environmental Concerns

A concern for this experiment is that it could be in the way of the custodians who use the room where this was conducted. It could also make a mess from spilling or could have a strong smell.

Experimental Design

Number Of Trials:

3

Number Of Subjects In Each trial:

7

When data will be collected:

Once a week for three weeks

Number of Observations:

Where will data be collected?:

Resources and Budget Table

Material	Size	Description	Quantity	Gotten From	Cost
container of skim milk	32oz	Hannafords store brand	1	Hannafords	1.45
container of 1% milk	32oz	Hood	1	Hannafords	1.59
container of 2% milk	32oz	Hood	1	Hannafords	1.59
container of whole milk	32oz	Hannafords store brand	1	Hannafords	1.45
container of fat free half & half	32oz	Hannafords store brand	1	Hannafords	2.29
container of regular half & half	32oz	Hannafords store brand	1	Hannafords	2.19
container of heavy cream	16oz	Hannafords store brand	2	Hannafords	2.49 each
cheesecloth	at least one
Cups	16oz	Plastic	24 pack	Walmart	1.28
scale		measures in grams	1	Borrow from Mr. Yahna	Free
Box	large enough to hold 21 cups	cardboard, with a lid	3	Available	Free
Bucket	gallon bucket	plastic with no holes	1	Available	Free
Tray	big enough to hold cheesecloth	plastic	1	Available	Free
Bungee Cord/Rubber Band	needs to fit around bucket		1-2	Available	Free
masking tape	roll		1	Available	Free
sharpie	thick pen	black	1	Available	Free

Time Line

Wednesday February 29 : Complete Design (home)
Friday March 2 : All Materials Collected and test run of set up (home and jbes)
Tuesday March 6 : Start experiment (come in early, do it in the morning)
Tuesday March 13 : First week data collection (jbes,morning)
Tuesday March 20 : Second week data collection (jbes, morning)
Tuesday March 27 : Third week data collection, finish experiment (jbes, morning)
Friday March 30 : Complete results and conclusions (home)

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Background Research

Curdling

• curds are dairy products
• curds are gotten by curdling milk and draining away the liquid part
• curds are made from the milk proteins combining to make a solid
• the liquid part left is the whey
• milk is made of two main proteins - whey and casein
• casein proteins for the curd, solid
• whey proteins for the remaining liquid
• curdling is often done using rennet or other acidic products such as vinegar and lemon juice
• curds are used often in the making of cheese, as well as custards,sauces and tofu
• curdles when a sour substance touches it
• lactic acid is created and milk sours and curdles
• when milk is stored for a long time, bacteria in the milk becomes harmful
• Also no clotting occurs above 60° to 65°C.
• The clot is softer at low temperatures
• tougher and stringy at high temperatures.
• could upset stomach if curdled milk is drank
• To change into curd. (definition)
• curdles happen when casein molecules aggregate or group

Milk

• Protein (casein) in milk causes it to curdle
• The composition of one serving of milk (whole dairy milk w/ 3.25% fat) includes:

Overall Composition:

Water: 215.50 g
Energy: 146 kcal
Carbohydrate: 11.03 g
Fat: 7.93 g
Protein: 7.86 g
Minerals (Ash): 1.68 g

Vitamins

Vitamin A: 68 µg
Thiamin (Vitamin B1): 0.107 mg
Riboflavin (Vitamin B2): 0.447 mg
Niacin (Vitamin B3): 0.261 mg
Pantothenic Acid (Vitamin B5): 0.883 mg
Pyridoxene (Vitamin B6): 0.088 mg
Cobalamin (Vitamin B12): 1.07 µg
Vitamin C: 0.0 mg
Vitamin D: 98 IU
Vitamin E: 0.15 mg
Folate: 12 µg
Vitamin K: 0.5 µg

Minerals (Ash):

Calcium: 276 mg
Copper: 0.027 mg
Iron: 0.07 mg
Magnesium: 24 mg
Manganese: 0.007 mg
Phosphorus: 222 mg
Potassium: 349 mg
Selenium: 9.0 µg
Sodium: 98 mg
Zinc: 0.98 mg

• whey makes up 20% of the protein in milk by weight

Pasteurized Milk

• for this experiment we will be using different percents of cow milk that has been pasteurized
• pasteurization is a process that involves heating the milk to a certain temp for a certain length, and then cooling it immediately
• this process slows microbial growth in the food
• is not intened to kill all micro-organisms in food
• it reduces the number of pathogens so the milk is less likely to cause disease
• (pathogens are germs)
• some dairy products may be superheated to make sure that all pathogens are destroyed
• cream was pasteurized to help keep butter fresh
• pasteurizing milk helps it to last longer
• regular pasteurized milk lasts about two to three weeks
• ultra-pasteurized milk can last much longer, two to three months
• there are two main types of pasturization:

-Hight Temperature Short Time (HTST)
this helps to extend shell life (esl) meaning it helps to make it last longer
-Ultra High Temperature (UHT)

• pasteruization uses temps under boiling
• at boiling, casein molecules group together, or curdle

References

__http://en.wikipedia.org/wiki/Pasteurization__
__http://en.wikipedia.org/wiki/Curd__
__http://en.wikipedia.org/wiki/Curdling__

__http://www.sritweets.com/milk-curdle-milk-curdle-bacteria-present-milk/__
__http://chestofbooks.com/food/science/Experimental-Cookery/Coagulation-Of-Milk.html#ixzz1mJJQpGzH__
__http://www.thefreedictionary.com/curdled__
__http://wiki.answers.com/Q/What_is_cow_milk_made_of#ixzz1mURwkDMV__
__http://en.wikipedia.org/wiki/Pasteurization__

Detailed Procedure

1. Gather all of our materials.
2. Bring materials to boiler room.
3. Pour each type of dairy product into it’s own separate cup, three cups for each dairy product.
4. Label each cup with product and week using the tape and sharpie.
5. Place all full cups for week one into a cardboard box.
6. Use tape and sharpie to label box “week one” on both the lid and side.
7. Place all full cups for week two into a second cardboard box.
8. Label this box “week two” on lid and side using sharpie and tape.
9. Put all remaining cups (for third week) into the third box.
10. Label this box “week three” with the sharpie and tape on both the lid and side.
11. Cover all of the boxes and line up on the side of the boiler room wall.
After one week of time...
12. Wash the cheesecloth with water, and wring out so its only damp (not dripping wet, but not dry).
13. Take one cup out of the “week one” box.
14. Have one person hold cheesecloth over a bucket while the other person dumps cup through it. Make sure the cheesecloth is taut, you might need a rubber band or bungee cord to do this.
15. Leave or hold the cheesecloth stretched taut over the bucket for 2 minutes, allowing whatever liquid (whey) to drip into the bucket.
16. After 2 minutes of time, place cheesecloth with curdles onto tray and then onto scale.
17. Record the weight in grams.
18. Record the data in a notebook, being sure to include week, dairy product and weight in grams.
19. List any observations in the notebook as well. Include things like appearance, smell, comments on the process, problems or difficulties, etc.
20. Take a picture of curds as well as a few of the process.
21. Wash cheesecloth like before. Rinse in water, making sure all debris from last product is off. Wring it out so it is only damp.
22. Repeat steps 13 through 21 with each cup in the “week one” box.
23. After another week of time, 14 days in total, repeat steps 12 through 21. This time use the cups from the box labeled “week two”.
24. After a third week of time, 21 days in total, repeat steps 12 through 21. This time use the cups from the box labeled “week three”.

Diagram

Photo List

All dairy products first day
All dairy products after one week
All dairy products after two weeks
All dairy products after three weeks
boxes in boiler room with lid on and off
curdles on scale
pouring milk into cheesecloth
washing cheesecloth
recording date in notebook
close up of curds

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Results

It was determined that the 2% milk produced the most curds, weighing in at 273.4 grams. Next was skim milk weighing 223.9 grams and then heavy cream weighing 190 grams. Fourth in weight was 1% milk which weighed 174.4 grams. Fifth heaviest weighed 163.2 grams which was whole milk, while sixth heaviest, regular half and half, weighed 134 grams. The last heaviest, or dairy product that produced the lightest mass of curds, was fat free half and half having a total weight of 96.8 grams.

All Raw Data

Data analysis spreadsheets available upon request

Graphs

https://docs.google.com/spreadsheet/pub?key=0AgwHhmyZZG__dFFNbGU0UllkQ1RHTE9ld2Y1dWV1TWc&output=html

https://docs.google.com/spreadsheet/pub?key=0AgwHhmyZZG__dEVVd1VDUFNzUEhZRmpSMW5fS0JpSnc&output=html

https://docs.google.com/spreadsheet/pub?key=0AgwHhmyZZG__dGdZdzlySFlhWU5FMkE0TWREcFNVTEE&output=html

https://docs.google.com/spreadsheet/pub?key=0AgwHhmyZZG__dHZXcWg4QlVJeFU1cEV4ZXRKVmpDOHc&output=html

https://docs.google.com/spreadsheet/pub?key=0AgwHhmyZZG__dEVFaFVfaDJyRU5qQ1JiVnNsMWtFY3c&output=html

https://docs.google.com/spreadsheet/pub?key=0AgwHhmyZZG__dGtuQXdHQnRZNnlOUFJvRGI3blhtQXc&output=html

https://docs.google.com/spreadsheet/pub?key=0AgwHhmyZZG__dGE2VXVQREcxcnFIN2hsTkl2RXBQcWc&output=html

Photos

Setting Up the Experiment in the Boiler Room

Labeling the Cups

All Three Boxes With Cups Inside

Boxes in Boiler Room, One for Each Week

Heavy Cream After One Week

Skim Milk, Week One

Curds on Cheesecloth Stretched Over Bucket

Week Two Box

Skim Milk, Week Two

Curds On Cheesecloth

Pouring Onto Cheesecloth

Week Three Box

Heavy Cream With Mold

Hard Yellow Crust On Top

More pictures available upon request

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Data Analysis

Conclusion

An experiment was conducted to see which dairy product produced the largest mass of curds. The question asked was “how does the percentage of fat in dairy products affect the rate it curdles at and the amount of curds it produces?” The dependent variable was the amount of curdles, and the independent variable was the type of dairy product. It was found that over 3 weeks, the 2% milk produced the largest mass of curds. The 2% milk had a total mass of 273.4 grams, next followed by the skim milk with 223.9 grams, and the dairy product that produced the third highest amount of curds was heavy cream with 190 grams. It was inferred that the curdles were caused by the casein proteins and that the milkfat actually kept the curds from forming. It is concluded that the percentage of fat in dairy products does not affect the rate dairy products curdle at.

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Discussion

An experiment was conducted to determine which type of dairy product produced the most curds after three weeks of time. The total weights were found by adding all three weeks weights together. Each product was weighed once after one week, two weeks and then three weeks. It was determined that 2% produced the most curds, weighing in a 273.4 grams. The hypothesis was that whole milk would produce the most curds, which was incorrect. Whole milk was actually third to last in weight, weighing only 163.2 grams. This hypothesis was incorrect because it was later learned that the casein proteins are what produce the curds and not milkfat. There was no noticeable relationship between the independent and dependent variables.Some dairy products started producing curds for the first week but by the third they had returned to liquid. For other dairy products it was the opposite, gradually increasing in curd mass as time went on.
While the experiment was being planned it was undecided where it would take place. Once a place was found, it turned out to be a good location. Before the start of the experiment, a concern was that it would smell terribly and cause its surroundings to stink as well. Precautions were taken, such as placing the dairy products away from high traffic areas and keeping them in boxes. It was discovered after the experiment began that stink would not be a problem. A problem that was encountered was using the cheesecloth. It needed to be cut to fit on the drainage bucket doubled up to hold the curds. It also had to be washed after each week, which took time and was messy. In a future experiment it would be wise to find a good place to conduct it since it does take up room and can be fairly messy. It would also be easier to have more cheesecloth so it would not have to be reused.
In order for this experiment to be conducted, research needed to be gathered on what dairy products produced curdles and about how long it took them to. After the experiment started more research was done to learn why things were happening. A scale was necessary for this experiment because without it there would be no way to collect data. The information learned through this experiment could be used by others, such as scientists, using dairy products or curds in an experiment. The graphs that were created could be used to learn when each dairy product curdles, and how much it produces, which can be used if someone needs to plan when they can have curds by or if they require a certain amount. This information could also help to create a more efficient way to produce curds that are needed for whatever reason, such as recipes.

Benefit to Community and/or Science

This experiment will benefit anyone in the future that might need either curds or whey or is using dairy products. The data can show how long it takes a product to curdle and how much it will produce. This information might help other scientists conducting a similiar experiment or another that simply involves whey proteins, casein proteins, curds or dairy. This could also help those who use dairy products or curds in recipes, such as a cook.

Abstract

This experiment was chosen to be conducted because there were curiosities about whether the fat in dairy products affected the amount of curds that product produced. An experiment was conducted to see which dairy product produced the largest mass of curds. The question asked was “how does the percentage of fat in dairy products affect the rate it curdles at and the amount of curds it produces?” The dependent variable was the amount of curdles, and the independent variable was the type of dairy product. It was found that over 3 weeks, the 2% milk produced the largest mass of curds. The 2% milk had a total mass of 273.4 grams, next followed by the skim milk with 223.9 grams, and the dairy product that produced the third highest amount of curds was heavy cream with 190 grams. It was inferred that the curdles were caused by the casein proteins and that the milkfat actually kept the curds from forming. It is concluded that the percentage of fat in dairy products does not affect the rate dairy products curdle at.